It is known from German Patent Publication D 2,423,454 (Riha et al.), published on Dec. 9, 1982, and from German Patent Publication DE 4,405,778 (Haussler et al.), published on Aug. 3, 1995, that a leno selvedge forming device also referred to a selvedge rotor is equipped with a leno disk that may be provided with a gear rim and is equipped with eyelets or rather with two thread guide channels positioned diametrically opposite each other and passing through the circular surface of the leno disk. Each of these eyelets or guide channels guide one leno thread. German Patent Publication D 4,405,778 corresponds in part to U.S. Pat. No. 5,524,678 (Haussler et al.).
For a proper leno selvedge formation it is necessary that each leno thread is detoured twice by about 90.degree. on its way from the leno thread supply spool to the leno selvedge as the thread passes through the eyelet or guide channel of the leno disk. There is a problem especially in connection with the use of delicate leno threads because these threads tent to break when they are diverted by the leno disk.
From German Patent Publication DE 4,405,777 (Haussler et al.) also corresponding in part to U.S. Pat. No. 5,524,678 (Haussler et al.) it is known to provide the leno disk with eyelets for guiding the leno thread. However, in operation the leno disk performs a full revolution in one direction and again a full revolution in the opposite direction, whereby the leno thread is temporarily tensionless which can cause kinking of the thread at the moment of direction reversal of the leno disk rotation. Such kinking takes place at each edge of the eyelet namely at its entrance side and at its exit side. These features of the prior art leave room for improvement especially with regard to handling the leno threads more gently for reducing wear and tare not only of the leno threads but also of the leno disk itself particularly the thread guide eyelets in the leno disk.
It is known from U.S. Pat. No. 5,524,678 (Haussler et al.) and from German Patent Publication D 2,515,961 (Kovar) to treat the leno threads more gently by an elongated eyelet or eyelets in the leno disk or ring. While this solution provides a relatively gentle treatment of the leno thread, it does reduce the length of the leno stroke of the leno disk for the formation of the leno shed.
U.S. Pat. No. 4,103,716 (Cornellier) discloses a leno motion device with thread tensioning levers to take up the slack when the leno disk reverses directions.
German Patent Publication 2,134,361 (Svaty) published on Mar. 2, 1972 discloses an apparatus for applying a breaking action to a leno thread which travels through an eyelet formed by a wire.
The above discussed prior art leaves room for improvement especially with regard to the gentle treatment of delicate leno threads and with regard to providing the required guiding of the leno threads.